From mboxrd@z Thu Jan  1 00:00:00 1970
From: zhangyanfei <zhangyanfei@cn.fujitsu.com>
Subject: Re: [PATCH 1/2] x86/kexec: VMCLEAR vmcss on all cpus if necessary
Date: Wed, 31 Oct 2012 09:52:28 +0800
Message-ID: <5090845C.6060508@cn.fujitsu.com>
References: <5080E813.7030302@cn.fujitsu.com> <5080E8BF.3020506@cn.fujitsu.com> <20121031001822.GA21986@amt.cnet>
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Cc: x86@kernel.org, kexec@lists.infradead.org,
	Avi Kivity <avi@redhat.com>, linux-kernel@vger.kernel.org,
	"kvm@vger.kernel.org" <kvm@vger.kernel.org>
To: Marcelo Tosatti <mtosatti@redhat.com>
Return-path: <linux-kernel-owner@vger.kernel.org>
In-Reply-To: <20121031001822.GA21986@amt.cnet>
Sender: linux-kernel-owner@vger.kernel.org
List-Id: kvm.vger.kernel.org

=E4=BA=8E 2012=E5=B9=B410=E6=9C=8831=E6=97=A5 08:18, Marcelo Tosatti =E5=
=86=99=E9=81=93:
> On Fri, Oct 19, 2012 at 01:44:31PM +0800, Zhang Yanfei wrote:
>> This patch provides a way to VMCLEAR vmcss related to guests
>> on all cpus before executing the VMXOFF when doing kdump. This
>> is used to ensure the VMCSs in the vmcore updated and
>> non-corrupted.
>>
>> Signed-off-by: zhangyanfei <zhangyanfei@cn.fujitsu.com>
>> ---
>>  arch/x86/include/asm/kexec.h |    2 ++
>>  arch/x86/kernel/crash.c      |   27 +++++++++++++++++++++++++++
>>  2 files changed, 29 insertions(+), 0 deletions(-)
>>
>> diff --git a/arch/x86/include/asm/kexec.h b/arch/x86/include/asm/kex=
ec.h
>> index 317ff17..fc05440 100644
>> --- a/arch/x86/include/asm/kexec.h
>> +++ b/arch/x86/include/asm/kexec.h
>> @@ -163,6 +163,8 @@ struct kimage_arch {
>>  };
>>  #endif
>> =20
>> +extern void (*crash_clear_loaded_vmcss)(void);
>> +
>>  #endif /* __ASSEMBLY__ */
>> =20
>>  #endif /* _ASM_X86_KEXEC_H */
>> diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
>> index 13ad899..7289976 100644
>> --- a/arch/x86/kernel/crash.c
>> +++ b/arch/x86/kernel/crash.c
>> @@ -16,6 +16,7 @@
>>  #include <linux/delay.h>
>>  #include <linux/elf.h>
>>  #include <linux/elfcore.h>
>> +#include <linux/module.h>
>> =20
>>  #include <asm/processor.h>
>>  #include <asm/hardirq.h>
>> @@ -30,6 +31,22 @@
>> =20
>>  int in_crash_kexec;
>> =20
>> +/*
>> + * This is used to VMCLEAR vmcss loaded on all
>> + * cpus. And when loading kvm_intel module, the
>> + * function pointer will be made valid.
>> + */
>> +void (*crash_clear_loaded_vmcss)(void) =3D NULL;
>> +EXPORT_SYMBOL_GPL(crash_clear_loaded_vmcss);
>> +
>> +static void cpu_emergency_clear_loaded_vmcss(void)
>> +{
>> +	if (crash_clear_loaded_vmcss &&
>> +	    cpu_has_vmx() && cpu_vmx_enabled()) {
>> +		crash_clear_loaded_vmcss();
>> +	}
>> +}
>> +
>=20
> Are all this checks necessary?=20
>=20
> if (crash_clear_loaded_vmcss)
> 	crash_clear_loaded_vmcss();
>=20
> Should be enough ? (callback only set if kvm-vmx module loaded).

Hmm, it is enough. Thanks.

>=20
>>  #if defined(CONFIG_SMP) && defined(CONFIG_X86_LOCAL_APIC)
>> =20
>>  static void kdump_nmi_callback(int cpu, struct pt_regs *regs)
>> @@ -46,6 +63,11 @@ static void kdump_nmi_callback(int cpu, struct pt=
_regs *regs)
>>  #endif
>>  	crash_save_cpu(regs, cpu);
>> =20
>> +	/*
>> +	 * VMCLEAR vmcss loaded on all cpus if needed.
>> +	 */
>> +	cpu_emergency_clear_loaded_vmcss();
>> +
>>  	/* Disable VMX or SVM if needed.
>>  	 *
>>  	 * We need to disable virtualization on all CPUs.
>> @@ -88,6 +110,11 @@ void native_machine_crash_shutdown(struct pt_reg=
s *regs)
>> =20
>>  	kdump_nmi_shootdown_cpus();
>> =20
>> +	/*
>> +	 * VMCLEAR vmcss loaded on this cpu if needed.
>> +	 */
>> +	cpu_emergency_clear_loaded_vmcss();
>> +
>>  	/* Booting kdump kernel with VMX or SVM enabled won't work,
>>  	 * because (among other limitations) we can't disable paging
>>  	 * with the virt flags.
>> --=20
>> 1.7.1
>>